Method for producing ferrite thin film body

ABSTRACT

A method for producing a ferrite thin film body is provided which comprises the steps of separately applying each of the metals composing the ferrite in layers on a non-magnetic heatresistant substrate, subjecting the metallic layers to a diffusion reaction under inert gas at an elevated temperature to produce a diffused solid solution, and subjecting the diffused solid solution to oxidation at an elevated temperature for a time period sufficient to change the solid solution to a ferrite body.

United States Patent 1191 Kobayashi et al.

[ Oct. 2, 1973 METHOD FOR PRODUCING FERRITE THIN FILM BODY [75]Inventors: Seihin Kobayashi; Michihiro Torii;

Katsuyuki Oshima, all of Hamana-gun Shizuoka-ken, Japan [73] Assignee:Fuji Denki Kagaku Kabushiki Kaisha, Tokyo, Japan 221 Filed: June 8,1971

21 Appl.No.: 151,069

[30] Foreign Application Priority Data June 11, 1970 Japan 45/50454 521U.S.Cl. 204 31 R,ll7/62, 148/121, 204/192 511 1111. C1. ..C23b 5/52 [58]Field of Search 1 1 7 6 2 ,l 1111, 1481121 [56] References Cited UNITEDSTATES PATENTS 6/1948 Williams 204/37 R 9/1964 Banks et al.

3,625,849 12/1971 Rogalla 204/37 R 3,549,428 12/1970 Lommel 148/121FOREIGN PATENTS QR APPLICATIONS 1 153,342 12/1961 U.S.S.R 204/37 R OTHERPUBLICATIONS Koretzky, H. Electrodeposition of Permanent MagneticMaterials. IBM Technical Disclosure Bulletin,

Vol. 6, No. 8, 1/64. 204/37R.

Primary Examiner-John H. Mack Assistant Examiner--W. 1. Solomon,AztorneyEliot S. Gerber [57] ABSTRACT 9 Claims, 1 Drawing Figure METHODFOR PRODUCING FERRITE THIN FILM BODY This invention relates to a methodfor producing a ferrite thin film body, to be used mainly as memoryelements, and more particularly to a method wherein each of the metalscomposing the ferrite is separately applied, in layers, on anon-magnetic heat-resistant substrate and then are subjected separatelyto diffusion and oxidizing reactions.

Conventionally, vacuum evaporation and a spattering method have beenused to produce ferrite thin film body on a non-magnetic heat-resistantsubstrate, the substrate having, for example, the form of a wire or aplate. In the vacuum evaporation method, the metals composing theferrite are heated enough to be evaporated and are solidified, undervacuum, on the substrate to form alloy layers thereon. The alloy layersare subjected to an oxidizing reaction to form the ferrite thin filmbody on the substrate.

In the spattering method, positive ions generated by a cold cathodedischarge in an inert gas are collided against a ferrite body and,thereby, the spattered metals composing the ferrite are deposited on thesubstrate to form a ferrite thin film body thereon.

But, many disadvantages have been experienced in the ferrite thin filmbodies produced in accordance with the above-mentioned methods. Firstly,as each of the metals composing the ferrite exists on the substrate inits amorphous state, the density of the crystallized particles is low,sintering reaction is delayed, the demagnetizing field becomes strong,and the ratio of input/output shows a very undesirable value. Secondly,in the oxidizing process, the metals composing the ferrite may separatefrom the substrate. Thirdly, the surface of the produced ferrite thinfilm body is not even. Fourthly, it is very difficult to reproduce theferrite thin film body of same composition.

Furthermore, it seems that the undesirable properties of theconventional ferrite thin film bodies are caused by fine cracks formedon the surface of the ferrite thin film body while the metals composingthe ferrite on the substrate is concurrently subjected to diffusion andoxidation reactions.

Accordingly, these conventional methods are undesirable and are notacceptable to produce the ferrite thin film body of high reliability.

An objective of the presentinvention is to provide a method forproducing a ferrite thin film body of high reliability and free from theabove-mentioned disadvantages.

According to the present invention, the method for producing ferritethin film body comprises the step of separately applying each of themetals composing the ferrite in layers on a non-magnetizedheat-resistant substrate, subjecting the metallic layers to a diffusionreaction under inert gas at an elevated temperature to form a diffusedsolid solution, and subjecting the diffused solid solution to oxidationat an elevated temperature for a time period sufficient to change thesolid solution to a ferrite body.

In order to separately apply each of the metals composing the ferrite inlayers on the substrate, conventional methods of electric plating,vacuum evaporation, cold cathode discharge spattering or the like can besuccessfully employed. Preferably, the substrate is made of a platinumwire or an alumina-ceramic wire.

In the diffusion process, the metallic layers composing the ferrite onthe substrate are exposed to an inert gas at an elevated temperature soas to change the metallic layers to a solid solution. During thediffusion process, an electric current is applied toboth of the metalliclayers and the substrate.

After the diffusion reaction, the diffused solid solution on thesubstrate is reacted with oxygen .at an elevated temperature, for aperiod long enough to change the diffused solid solution to ferrite thinfilm body.

By separately applying each of the ferrite composing metals in layers tothe substrate, it becomes easy to control the ratio of composing metalsand, thereby, to reproduce ferrite thinflm bodies having the samecompositions. Furthermore, as the metallic layers are subjected to thediffusion reaction (to make the diffused solid solution before theoxidizing process) many advantages are obtained, such that (a) theferrite thin film body is even and dense, (b) the ferrite thin film bodywill not be separated from the substrate, providing a reliable ferritethin film body, (c) the sintering reaction is speedily effected, and (d)the demagnetizing field is reduced to remarkably improve the ratio ofinput/output.

Taking an example of Cu--Mn ferrite, which is widely known as one of thematerials having a rectangular magnetic characteristic, an. embodimentof the present invention shall be described hereinafter with referenceto the drawing, in which:

The single drawing is a graph showing the characteristics of pulse drivecurrents applied to a CuMn ferrite thin film body, produced inaccordance with the present invention.

EXAMPLE Platinum wire is used as a substrate. Layers of metal areapplied to the wire, by electrochemical plating, in the order of Fe(Iron), Cu (Copper), and Mn (Manganese). The following table shows theconditions and The plated platinum wire was then placed into a chamberfilled with inert gas (containing oxygen less than 2%), such as nitrogengas or argon gas. The temperature in the chamber was elevated, during 1hour, up to a temperature higher than 800C but lower than 1083C, whichis the melting point of Cu. Keeping the chamber at the elevatedtemperature for an additional 30 minutes, electric current of 1-3 amperewas applied to the platinum wire, as the cathode, and to the platedmetallic layers. A diffusion reaction occurred and the metal layers werechanged to a solid solution. Then the temperature inside the chamber waslowered to room temperature, the duration of the temperature loweringbeing 1 hour.

After the diffusion reaction step, the inert gas was removed and oxygensubstituted (purity of more than percent). The chamber was then heatedduring one hour up to 1 150C. The oxidization of the diffused solidsolution was effected at the elevated temperature for an additionalminutes, during which the solid solution was changed to ferrite thinfilm body. Thereafter, the produced ferrite thin film body was graduallycooled in air, the cooling occurring for a period of one hour.

As shown in the drawing, the Cu--Mn ferrite film body, produced inaccordance with the method of the present invention, has a fasterswitching time and an excellent rectangular magnetic characteristic andis sufficiently good to be used for magnetic memory elements.

As disclosed above, the method according to the present inventionprovides reliable ferrite thin film body having excellent magneticcharacteristics.

Although the present invention has been described with reference to thepreferred embodiment shown in the drawing, many modifications andalternations may be made within the spirit of the present invention.

We claim:

1. A method for producing a CuMn ferrite thin film body on anon-magnetic heat-resistant substrate comprising the steps of applyingFe, Cu, and Mn respectively in layers on said substrate, subjecting saidmetallic layers to a diffusion reaction under inert gas at a temperaturehigher than 800C but lower than 1083C, said metallic layers beingthereby changed to a diffused solid solution, and subjecting said solidsolution to oxidation at a temperature higher than 1083C for asufficient time to change said solid solution to a ferrite body.

2. A method as claimed in claim 1, wherein said metallic layers and saidsubstrate as the cathode are supplied with electric current while theyare subjected to said diffusion reaction.

3. A method as claimed in claim 2, wherein said metallic layers areformed on said substrate, such as wire or plate, by electrochemicalplating.

4. A method as claimed in claim 3, wherein said metallic layers areformed on said substrate, such as wire or plate, by vacuum evaporation.

5. A method as claimed in claim 2, wherein said metallic layers areformed on said substrate, such as wire or plate, by a spattering method.

6. A method for producing a CuMn ferrite thin film body on anon-magnetic heat-resistant substrate comprising the steps of platingFe, Cu, and Mn respectively in layers on said substrate, subjecting saidplated metallic layers to a diffusion reaction under inert gas at atemperature higher than 800C but lower than 1083C while said platedmetallic layers and said substrate as the cathode are supplied with anelectric current, said metallic layers being thereby changed to adiffused solid solution, and subjecting said solid solution to oxidationat a temperature higher than 1083C for a sufficient time to change saidsolid solution to a ferrite body.

7. A method as claimed in claim 5, wherein said substrate is a platinumwire.

8. A method as claimed in claim 5, wherein said substrate is analumina-ceramic wire.

9. A method as claimed in claim 6 wherein the layers are applied in theorder of Fe, Cu and Mn.

- UNITED STA'I'ES PATENT OFFICE CERTIFECATE OF CQRRECTION Ramon: No. 6 r00 Dated I October 2 1973 i Q seihin Kobayashi; Michihiro Torii; Katsuyuki Oshima It: is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

[30] Foreign Application Priority Data changed to v Y June 10, 1970 Jaan 49509 Signed and sealed this 19th day of February 19m.

(SEAL) Attest: v

EDWARD M.FLETCHE R,JR. c; MARSHALL DANN Attesting Officer Commissionerof Patents

2. A method as claimed in claim 1, wherein said metallic layers and saidsubstrate as the cathode are supplied with electric current while theyare subjected to said diffusion reaction.
 3. A method as claimed inclaim 2, wherein said metallic layers are formed on said substrate, suchas wire or plate, by electrochemical plating.
 4. A method as claimed inclaim 3, wherein said metallic layers are formed on said substrate, suchas wire or plate, by vacuum evaporation.
 5. A method as claimed in claim2, wherein said metallic layers are formed on said substrate, such aswire or plate, by a spattering method.
 6. A method for producing a Cu-Mnferrite thin film body on a non-magnetic heat-resistant substratecomprising the steps of plating Fe, Cu, and Mn respectively in layers onsaid substrate, subjecting said plated metallic layers to a diffusionreaction under inert gas at a temperature higher than 800*C but lowerthan 1083*C while said plated metallic layers and said substrate as thecathode are supplied with an electric current, said metallic layersbeing thereby changed to a diffused solid solution, and subjecting saidsolid solution to oxidation at a temperature higher than 1083*C for asufficient time to change said solid solution to a ferrite body.
 7. Amethod as claimed in claim 5, wherein said substrate is a platinum wire.8. A method as claimed in claim 5, wherein said substrate is analumina-ceramic wire.
 9. A method as claimed in claim 6 wherein thelayers are applied in the order of Fe, Cu and Mn.